Bio Unit 7 Intracellular Compartments And Protein Sorting

Front 1

Organization within eukaryotic cell is random (T/F)

Back 1

False

Front 2

What is cytoskeleton important in?

Back 2

- cell shape
- cell motility
- movement / position of organelles
- movement of materials within cell
- movement of chromosomes during mitosis

Front 3

What are the 3 ways to import proteins onto organelles?

Back 3

-Transport through nuclear pores
-Transport across membranes
-Transported by vesicles

Front 4

What is protein sorting?

Back 4

transfer of proteins into compartments where they are needed

Front 5

Synthesis of virtually all proteins starts in cytosol, on?

Back 5

Free ribosomes

Front 6

What is the signal sequence?

Back 6

Stretch of amino acids, 15-60 AAs long, that directs proteins to particular organelles by binding to it

Front 7

Signal sequences for?

Back 7

nucleus, mito/chloro, peroxisomes or ER

Front 8

Signal sequences are usually removed after sorting (T/F)

Back 8

True

Front 9

When does the protein go to the wrong "address"?

Back 9

When deletion occurs, or when sequence goes to a wrong protein

Front 10

A nucleus has a double membrane called?

Back 10

The nuclear envelope

Front 11

Proteins to be imported to the nucleus have a ______ localization sequence.

Back 11

nuclear

Front 12

Do nuclear transport receptors get recycled?

Back 12

Yes! Nuclear transport receptors bind with the nuclear protein with the nuclear localization signal and brings it through the nuclear pore. The receptor then goes back through the pore and binds with a new protein.

Hint 12

Front 13

What are nuclear pores?

Back 13

Gateway to the nucleus

Front 14

_______ molecules (even _______ proteins) freely pass through nuclear pores.

Back 14

Small, small

Front 15

The passage of a larger protein is an ______ process. Which means?

Back 15

Active.

Energy is required

Front 16

What is a nuclear localization signal?

Back 16

An amino acid sequence that ‘tags’ a protein for import into the nucleus by nuclear transport

Front 17

What is a nuclear export signal?

Back 17

tags a protein for export

Front 18

What moves out of a nucleus?

Back 18

Mature, properly made mRNA, ribosomal RNA

Front 19

What moves into the nucleus?

Back 19

-histones
-ribosomal proteins
-proteins required for transcription & DNA replication
-dNTPs, rNTPs (purine, pyrimidine)

Front 20

Chloroplast has a third membrane (T/F)

Back 20

True

Front 21

What is chloroplast's 3rd membrane called?

Back 21

Thylakoids

Front 22

Mitochondria and chloroplasts have their own genomes and ribosomes, most of their proteins are encoded by _______ genome, so it must be _______.

Back 22

Nuclear, imported

Front 23

Proteins destined for mitochondria/chloroplasts are made by ________ in the cytosol.

Back 23

Free ribosomes

Front 24

Proteins must be _________ to be imported, then upon import, fold and have the signal sequence removed (import of proteins into mitochondria)

Back 24

unfolded

Hint 24

Front 25

Where does the signal sequence attach to on the protein going into the mitochondria/chloroplast?

Back 25

N terminus

Front 26

Proteins must be moved across both ______ and ______ membranes at special sites where layers are in contact.

Back 26

outer, inner

Front 27

Explain the process of import of a protein into mitochondria.

Back 27

1. signal sequence (SS) binds at N terminus of the protein (protein is unfolded)
2. SS binds with receptor protein on the outer membrane
3. The protein translocation moves the protein to the contact site
4. Protein comes off the receptor protein and goes through the contact site (both membranes)
5. Once in the mitochondrial matrix, the protein folds and the signal sequence is cleaved
6. Now the protein is mature

Front 28

Synthesis of all proteins starts on free ribosomes (T/F)

Back 28

True

Hint 28

Front 29

ER is most extensive of endomembrane system (T/F)

Back 29

True

Front 30

ER serves as entry point for which organelles?

Back 30

-proteins for ER
-Golgi
-lysosomes
-endosomes
-cell surface
-secretory proteins

Front 31

What is the lumen of the ER?

Back 31

The space enclosed by the membrane of the ER

Front 32

Once in ER (in membrane or lumen), proteins will never re-enter cytosol (T/F).

Back 32

True

Front 33

What are the 2 types of proteins transferred to the ER?

Back 33

-Water soluble proteins translocated completely across into the lumen
-Transmembrane proteins translocated only partially across

Front 34

What are water soluble proteins destined for?

Back 34

Destined for secretion or the lumen of an organelle

Front 35

What are transmembrane proteins destined for?

Back 35

Destined for plasma membrane, ER membrane, or membrane of another organelle

Front 36

The ER signal sequence and an _______ direct ribosome to the ER

Back 36

Signal recognition particle (SRP)

Hint 36

Front 37

The signal recognition particle (SRP) go to the SRP receptor in the ER membrane. What happens next?

Back 37

SRP is displaced and recycled. The ER signal sequence on the growing polypeptide chain binds to the translocation channel and the protein goes through it into the ER lumen

Hint 37

Front 38

The signal peptidase then closes the translocation channel. Mature soluble protein is now in the ER lumen (T/F)

Back 38

true

Front 39

What happens in a Single-Pass Transmembrane Proteins?

Back 39

The stop codon in the protein enables the signal peptidase to come early and close the translocation channel which essentially traps the protein within the double membrane.

This is called a mature transmembrane protein.

Hint 39

Front 40

What is a vesicular transport in respect to proteins?

Back 40

Transport vesicles carry soluble proteins, and membrane proteins between compartments

Front 41

What are soluble proteins?

Back 41

It's mature proteins in the lumen of an organelle

Front 42

What are vesicular transport in general?

Back 42

Outward from ER, to the Golgi, to other organelles or plasma membrane

Inward from plasma membrane, endosome, lysosome

Hint 42

Front 43

Vesicle budding is driven by formation of what?

Back 43

protein coat

Front 44

What is an example of vesicle budding?

Back 44

Clathrin-Coated Vesicles

Front 45

What is Clathrin coated vesicles?

Back 45

- mediate transport from outward face to Golgi and inward from plasma membrane
- clathrin forms ‘basket’ that gives vesicle shape
- ‘adaptins’ recognize and capture specific cargo for transport

Hint 45

Front 46

What are the functions of the rough ER?

Back 46

Synthesize proteins for:

-secretion/export
-membrane insertion
-lysosomes

Front 47

Golgi apparatus function?

Back 47

Kinda like a mailbox office. Collects, packages, and distributes.

-Modification of new proteins arriving from ER:
-peptide chains shortened by proteases (enzyme that breaks down proteins and peptides)
-amino acids modified
-CHO groups that were added in ER modified or removed
-glycosylation (adding sugar to protein)
-different CHO groups added to different AAs (ser, thr) “O-linked glycosylation”

Front 48

Where does the secretory pathway occur?

Back 48

ER

Front 49

Most proteins are covalently modified in the ER (T/F)

Back 49

True

Front 50

Formation of what bonds happens between proteins in the ER?

Back 50

disulfide (very strong)

Front 51

What do the additions of sugar groups do in the secretory pathway?

Back 51

various functions depending on protein.

-protect protein from degradation
-keep protein in ER until properly folded
-help direct protein to proper organelle (act as transport signal for packaging into appropriate vesicles)
-if displayed on cell surface, cell-cell recognition

Front 52

What is glycosylation?

Back 52

As a growing peptide enters ER, ‘prefab’ carbohydrate group attaches to amino (NH2) groups of asparagine (Asn) side chains
“N-linked glycosylation”

Hint 52

Front 53

Greater protein flux increases what?

Back 53

The size of ER

Front 54

Only properly folded proteins are allowed to leave the ER (T/F)

Back 54

True

Hint 54

Front 55

What is greater protein flux?

Back 55

When protein production exceeds capacity to keep up with folding

Front 56

What happens during greater protein flux?

Back 56

Misfolded proteins accumulate and signals to make more ER

Front 57

What happens if cells still can't keep up?

Back 57

The unfolded protein response (UPR) will trigger cell death/apoptosis

Front 58

What happens during the modification and sorting in the Golgi Apparatus?

Back 58

Organized into functionally distinct compartments with cis (entry) face closest to ER, trans (exit) face at other end

Front 59

Series of flattened sacs in the golgi apparatus are called?

Back 59

cisternae

Front 60

What is cis?

Back 60

newly formed, face closest to the ER

Front 61

What is trans?

Back 61

breaking away, faces the end further from the ER

Front 62

The most complex polysaccharides synthesized in?

Back 62

Golgi apparatus:

-glycos amino glycans in extracellular matrix (animals)
-pectins, hemicellulose (plant cell walls)

Front 63

What is phagocytosis?

Back 63

Allows cells to take up large particles (ie. yeast being engulfed by bigger cell)

Front 64

What is constitutive secretion?

Back 64

Proteins are sorted into vesicles in the Golgi and move directly to the cell surface and fuse with the plasma membrane (exocytosis), resulting in the release of soluble proteins to the plasma membrane.

UNREGULATED membrane fusion.

Front 65

What is regulated secretion?

Back 65

Differs in that the proteins are stored in secretory vesicles that later fuse with the plasma membrane in response to a specific signal.

REGULATED membrane fusion

Front 66

What are Endocytic Pathways?

Back 66

The process of taking substances into cell by surrounding them with membrane (absorb or engulf)

Front 67

What are the 2 main types of vesicles based on the size formed?

Back 67

Pinocytosis and phagocytosis

Front 68

What is pinocytosis? [endocytic]

Back 68

"cell drinking" - tiny vesicles formed called endosomes which is done by all eukaryotic cells.

-‘bulk’ – any molecules present in enclosed fluid enter cell

Hint 68

Front 69

Phagocytosis is? [endocytic]

Back 69

"Cell eating"- much larger vesicles called phagosomes. Only done by specialized cells.

-eats particles, other cells, debris

Hint 69

Front 70

What is endocytosis? And what happens?

Back 70

When eukaryotic cells take in extracellular molecules. The plasma membrane invaginates and pinches off cargo filled vesicles

Front 71

What are triskelions?

Back 71

3 legged thing that come together to form a cage made up of clathin

Front 72

What are receptor-mediated endocytosis?

Back 72

Process by which cells undergo endocytosis by the inward budding of plasma membrane vesicles containing proteins with receptor sites specific to the molecules being internalized

Hint 72

Front 73

Receptor-Mediated Endocytosis, e.g. LDL

Back 73

watch video on cd

Hint 73

Front 74

What are hydrolytic enzymes?

Back 74

In lysosomes that digest the particles of LDL. This creates what?

Hint 74

Free cholesterol

Front 75

Lysosomes are the site of cellular ________.

Back 75

Digestion